In Vitro and In Vivo Activities of Ciprofloxacin and Levofloxacin against an SHV-5 Extended-Spectrum ß-Lactamase-Producing Klebsiella pneumoniae Strain

Activities of ciprofloxacin and levofloxacin against an SHV-5 extended-spectrum ß-lactamase (ESBL)-producing Klebsiella pneumoniae strain were studied in vitro and in vivo in septic mice using a high inoculum. Susceptibility to ciprofloxacin and levofloxacin was independent of the inoculum size. In killing curve studies, after 24 hours the initial 7.69 log 10 CFU / ml increased in the control to 9.34, while it was reduced to 4.83 by ciprofloxacin and to 4.25 by levofloxacin. Mice were infected with 10 7 CFU / g of K. pneumoniae intraperitoneally. Treatment started 2 hours later, when the mean blood bacterial counts were 7.33 log 10 CFU / ml, and lasted for 26 hours from the time of infection. Blood bacterial count was reduced from 7.33 log 10 CFU / ml to 4.08 log 10 CFU / ml by ciprofloxacin (20mg / kg / 6 hours), and to 3.60 log 10 CFU / ml by levofloxacin (50 mg / kg / 6 hours) 8 hours after the infection, which differed significantly from the infected untreated group. Ciprofloxacin and levofloxacin prolonged significantly the survival of mice compared with the infected untreated group (p<0.001 for both groups). There were not significant differences either in the survival (p=1.0) or in the blood bacterial counts (p=0.216 after 8 hours) between ciprofloxacin and levofloxacin group. Based on these results both ciprofloxacin and levofloxacin could be alternative therapeutic agents for the infection caused by ESBL-producing Klebsiella strains.